研究成果

国際会議

  • Efficient Threshold Public Key Encryption from the Computational Bilinear Diffie-Hellman Assumption
    著者
    M. Ebina, J. Mita, J. Shikata, and Y. Watanabe
    会議名
    APKC 2021
    出版社
    ACM Press
    発行年
    2021
    To appear.
    Abstract

    In this paper, we show the first efficient threshold public-key encryption (TPKE) scheme under the difficulty of search problems. More specifically, our TPKE scheme simultaneously achieves: (1) Chosen ciphertext security (CCA security) under the computational bilinear Diffie-Hellman (CBDH) assumption in the standard model; (2) re-splittability, which is a useful property that makes partial secret keys refreshable; and (3) O(kappa)-bit ciphertexts and public keys. Most previous CCA-secure TPKE schemes rely on decisional complexity assumptions or random oracles. Although there exist CCA-secure TPKE schemes under the difficulty of search problems, all such schemes are inefficient or work over small plaintext spaces. Technically, we begin with a direct construction of a threshold identity-based key encapsulation mechanism (TIB-KEM) with a weak security notion. Then, we transform the weakly-secure TIB-KEM into a CCA-secure TPKE scheme via the tag-KEM/DEM approach.